scholarly journals NuSTAR and XMM–Newton observations of SXP 59 during its 2017 giant outburst

2019 ◽  
Vol 489 (1) ◽  
pp. 1000-1005
Author(s):  
Shan-Shan Weng ◽  
Ming-Yu Ge ◽  
Hai-Hui Zhao
Keyword(s):  
Magnetic Field ◽  
Pulse Shape ◽  
The Other ◽  
Limited Data ◽  
High Luminosity ◽  
Thermal Component ◽  
X Ray ◽  
Spectral Models ◽  
Dipole Magnetic Field ◽  
Energy Dependent

ABSTRACT The Be X-ray pulsar (BeXRP) SXP 59 underwent a giant outburst in 2017 with a peak X-ray luminosity of 1.1 × 1038 erg s−1. We report on the X-ray behaviour of SXP 59 with the XMM–Newton and NuSTAR observations collected at the outburst peak, decay, and the low luminosity states. The pulse profiles are energy dependent, the pulse fraction increases with the photon energy and saturates at 65 per cent above 10 keV. It is difficult to constrain the change in the geometry of emitting region with the limited data. Nevertheless, because the pulse shape generally has a double-peaked profile at high luminosity and a single peak profile at low luminosity, we prefer the scenario that the source transited from the super-critical state to the sub-critical regime. This result would further imply that the neutron star (NS) in SXP 59 has a typical magnetic field. We confirm that the soft excess revealed below 2 keV is dominated by a cool thermal component. On the other hand, the NuSTAR spectra can be described as a combination of the non-thermal component from the accretion column, a hot blackbody emission, and an iron emission line. The temperature of the hot thermal component decreases with time, while its size remains constant (R ∼ 0.6 km). The existence of the hot blackbody at high luminosity cannot be explained with the present accretion theories for BeXRPs. It means that either more sophisticated spectral models are required to describe the X-ray spectra of luminous BeXRPs, or there is non-dipole magnetic field close to the NS surface.

scholarly journals The braking index of PSR B0540−69 and the associated pulsar wind nebula emission after spin-down rate transition

2020 ◽  
Vol 494 (2) ◽  
pp. 1865-1870 ◽  
Author(s):  
L J Wang ◽  
M Y Ge ◽  
J S Wang ◽  
S S Weng ◽  
H Tong ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Energy Density ◽  
Observational Evidence ◽  
The Other ◽  
High Quality ◽  
X Ray ◽  
Dipole Magnetic Field ◽  
Pulsar Wind ◽  
The Magnetic Field ◽  
High Cadence

ABSTRACT In 2011 December, PSR B054−69 experienced a spin-down rate transition (SRT), after which the spin-down power of the pulsar increased by $\sim 36{{\ \rm per\ cent}}$. About 1000 d after the SRT, the X-ray luminosity of the associated pulsar wind nebula (PWN) was found to brighten by $32\pm 8{{\ \rm per\ cent}}$. After the SRT, the braking index n of PSR B0540−69 changes from n = 2.12 to 0.03 and then keeps this value for about five years before rising to n = 0.9 in the following years. We find that most of the current models have difficulties in explaining the measured braking index. One exceptive model of the braking index evolution is the increasing dipole magnetic field of PSR B0540−69. We suggest that the field increase may result from some instabilities within the pulsar core that enhance the poloidal component at the price of toroidal component of the magnetic field. The increasing dipole magnetic field will result in the X-ray brightening of the PWN. We fit the PWN X-ray light curve by two models: one assumes a constant magnetic field within the PWN during the brightening and the other assumes an enhanced magnetic field proportional to the energy density of the PWN. It appears that the two models fit the data well, though the later model seems to fit the data a bit better. This provides marginal observational evidence that magnetic field in the PWN is generated by the termination shock. Future high-quality and high-cadence data are required to draw a solid conclusion.

scholarly journals A systematic study of soft X-ray pulse profiles of magnetars in quiescence

2019 ◽  
Vol 485 (3) ◽  
pp. 4274-4286 ◽  
Author(s):  
Chin-Ping Hu ◽  
C-Y Ng ◽  
Wynn C G Ho
Keyword(s):  
Magnetic Field ◽  
Systematic Study ◽  
High Surface ◽  
The Other ◽  
Quiescent State ◽  
High Luminosity ◽  
X Ray ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Fourier Harmonics

Abstract Magnetars are neutron stars with extremely high surface magnetic fields. They show diverse X-ray pulse profiles in the quiescent state. We perform a systematic Fourier analysis of their soft X-ray pulse profiles. We find that most magnetars have a single-peaked profile and hence have low amplitudes of the second Fourier harmonics (A2). On the other hand, the pulsed fraction (PF) spreads over a wide range. We compared the results with theoretical profiles assuming various surface hotspot asymmetries, viewing geometries, and beaming functions. We found that a single value of the intensity ratio r between two antipodal hotspots is unable to reproduce the observed distribution of A2 and PF for all magnetars. The inferred r is probably anticorrelated with the thermal luminosity, implying that high-luminosity magnetars tend to have two symmetric hotspots. Our results are consistent with theoretical predictions, for which the existence of an evolving toroidal magnetic field breaks the symmetry of the surface temperature.

scholarly journals X-Ray Flares and Outflows Driven by Magnetic Interaction Between a Protostar and its Surrounding Disk

1997 ◽  
Vol 163 ◽  
pp. 717-718
Author(s):  
Mitsuru Hayashi ◽  
Kazunari Shibata ◽  
Ryoji Matsumoto
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Plasma Temperature ◽  
Magnetic Interaction ◽  
Central Star ◽  
X Ray ◽  
Mhd Simulations ◽  
Flare Loops ◽  
Hot Plasma ◽  
Dipole Magnetic Field

AbstractHere we present a model of hard X-ray flares and hot plasma outflows (optical jets) observed in protostars. Assuming that the dipole magnetic field of a protostar threads the protostellar disk, we carried out 2.5-dimensional magnetohydrodynamic (MHD) simulations of the diskstar interaction. The closed magnetic loops connecting the central star and the disk are twisted by the rotation of the disk. In the presence of resistivity, magnetic reconnection takes place in the current sheet formed inside the expanding loops. Hot, outgoing plasmoid and post flare loops are formed as a result of the reconnection. Numerical results are consistent with the observed plasma temperature (107 – 108K), the length of the flaring loop (1011 – 1012cm), and the speed of optical jets (200 – 400 km s−1 ).

scholarly journals Solar activity and solar oscillations

1997 ◽  
Vol 181 ◽  
pp. 277-285
Author(s):  
Y. Elsworth
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Radio Emission ◽  
Surface Temperature ◽  
The Sun ◽  
Solar Oscillations ◽  
Thermal Component ◽  
X Ray ◽  
Convective Flows ◽  
Wide Range

Helioseismology provides us with the tools to probe solar activity. So that we can consider how the solar oscillations are influenced by that activity, we first consider the phenomena that we associate with the active Sun. The surface of the Sun is not quiet but shows evidence of convection on a wide range of scales from a few hundred kilometres through to several tens-of-thousands of kilometres. The surface temperature shows signs of the convection structures with the temperature in the bright granules being some 100 K to 200 K hotter than the surrounding dark lanes. Sunspots, which are regions of high magnetic field that suppress convective flows, are clearly visible to even quite crude observations. They are several tens-of-thousands of kilometres in diameter and about 2000 K cooler than their surroundings. Ultraviolet and X-ray pictures from satellites show that the higher layers of the solar atmosphere are very non-uniform with bright regions of high activity. Contemporaneous magnetograms show that these regions are associated with sunspots. Flares - regions of magnetic reconnections - are seen at all wavelengths from X-ray through the visible to radio. They are the non-thermal component of the radio emission of the Sun. There are many other indicators of activity on the Sun.

scholarly journals LOW-MAGNETIC-FIELD MAGNETARS

2013 ◽  
Vol 22 (13) ◽  
pp. 1330024 ◽  
Author(s):  
ROBERTO TUROLLA ◽  
PAOLO ESPOSITO
Keyword(s):  
Magnetic Field ◽  
Magnetic Energy ◽  
Strong Field ◽  
Radio Pulsars ◽  
X Ray ◽  
Soft Gamma Repeaters ◽  
Dipole Magnetic Field ◽  
Standard Picture ◽  
Observational Status ◽  
Low Magnetic Field

It is now widely accepted that soft gamma repeaters and anomalous X-ray pulsars are the observational manifestations of magnetars, i.e. sources powered by their own magnetic energy. This view was supported by the fact that these "magnetar candidates" exhibited, without exception, a surface dipole magnetic field (as inferred from the spin-down rate) in excess of the electron critical field (≃ 4.4×1013 G). The recent discovery of fully qualified magnetars, SGR 0418+5729 and Swift J1822.3-1606, with dipole magnetic field well in the range of ordinary radio pulsars posed a challenge to the standard picture, showing that a very strong field is not necessary for the onset of magnetar activity (chiefly bursts and outbursts). Here we summarize the observational status of the low-magnetic-field magnetars and discuss their properties in the context of the mainstream magnetar model and its main alternatives.

Glass-Coated Cu-Mn-Ga Microwires Produced by Taylor-Ulitovsky Technique

2009 ◽  
Vol 152-153 ◽  
pp. 79-84 ◽  
Author(s):  
Joan Josep Suñol ◽  
L. Escoda ◽  
C. García ◽  
V.M. Prida ◽  
Victor Vega ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solid Solution ◽  
Curie Temperature ◽  
Energy Dispersive Spectroscopy ◽  
Room Temperature ◽  
Alloy Composition ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray ◽  
Low Magnetic Field

Glass-coated Cu-Mn-Ga microwires were fabricated by Taylor-Ulitovsky technique. By means of energy dispersive spectroscopy microanalysis, an average alloy composition of Cu56Ga28Mn16 was determined. The temperature dependence of magnetization measured at a low magnetic field showed the coexistence of two ferromagnetic phases. The Curie temperature of one phase is 125 K and above room temperature for the other one. X-ray diffraction at room temperature and at 100 K reflects the presence of the same three crystalline phases corresponding to the cubic B2 Cu-Mn-Ga structure as a main phase and the minor phases of fcc Cu rich solid solution with Mn and Ga and the monoclinic CuO.

Alignment of Primary Phase of a Binary Alloy during Solidification

2007 ◽  
Vol 26-28 ◽  
pp. 563-565
Author(s):  
Kazuhiko Iwai ◽  
Manabu Usui ◽  
Shigeo Asai
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
Diffraction Pattern ◽  
Primary Phase ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray ◽  
Specific Direction ◽  
Crystal Alignment ◽  
The Magnetic Field

A static magnetic field and an alternating current are imposed on a metallic alloy during solidification for a crystal alignment of the primary phase. A Sn-10%Pb is selected as a sample because its primary phase is expected to have an anisotropic nature in magnetic susceptibility. In the x-ray diffraction pattern of the sample solidified without the magnetic field, the first and second highest peaks are (101) and (211) planes. On the other hand, those solidified with the magnetic field are (200) and (220) planes which are magnetically preferred planes. That is, the primary phase crystals in the sample solidified with the magnetic field are aligned to the specific direction.

scholarly journals SMC X-3: the closest ultraluminous X-ray source powered by a neutron star with non-dipole magnetic field

2017 ◽  
Vol 605 ◽  
pp. A39 ◽  
Author(s):  
S. S. Tsygankov ◽  
V. Doroshenko ◽  
A. A. Lutovinov ◽  
A. A. Mushtukov ◽  
J. Poutanen
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
X Ray ◽  
Dipole Magnetic Field

scholarly journals Polarization of accreting X-ray pulsars – II. Hercules X-1

2020 ◽  
Vol 501 (1) ◽  
pp. 129-136
Author(s):  
Ilaria Caiazzo ◽  
Jeremy Heyl
Keyword(s):  
Quantum Electrodynamics ◽  
Pulse Shape ◽  
Main Peak ◽  
Polarization Angle ◽  
X Ray ◽  
Structure And Dynamics ◽  
Cyclotron Line ◽  
Magnetic Poles ◽  
Energy Dependent ◽  
Polarization Fraction

ABSTRACT We employ our new model for the polarized emission of accreting X-ray pulsars to describe the emission from the luminous X-ray pulsar Hercules X-1. In contrast with previous works, our model predicts the polarization parameters independently of spectral formation, and considers the structure and dynamics of the accretion column, as well as the additional effects on propagation due to general relativity and quantum electrodynamics. We find that our model can describe the observed pulse fraction and the pulse shape of the main peak, as well as the modulation of the cyclotron line with phase. We pick two geometries, assuming a single accretion column or two columns at the magnetic poles, that can describe current observations of pulse shape and cyclotron modulation with phase. Both models predict a high polarization fraction, between 60 and 80 per cent in the 1–10 keV range, that is phase and energy dependent, and that peaks at the same phase as the intensity. The phase and energy dependence of the polarization fraction and of the polarization angle can help discern between the different geometries.

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